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United States Patent |
5,002,553
|
Shiber
|
*
March 26, 1991
|
Atherectomy system with a clutch
Abstract
An atherectomy system for cutting an obstruction in a patient's vessel,
comprising a flexible guide-wire insertable into the vessel, a flexible
rotary-catheter being rotatably disposed and insertable into the vessel,
over the flexible guide-wire, a cutting means for cutting the obstruction,
at a distal end of the flexible rotaty-catheter, coupling means at the
proximal end of the flexible rotary-catheter for engaging a drive means
and at least one torque limiting clutch interposed between the drive means
and the cutting means, limiting the torque transmitted distally.
Inventors:
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Shiber; Samuel (Woburn, MA)
|
Assignee:
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Surgical Systems & Instruments, Inc. (Mundelen, IL)
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[*] Notice: |
The portion of the term of this patent subsequent to November 28, 2006
has been disclaimed. |
Appl. No.:
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323328 |
Filed:
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March 13, 1989 |
Current U.S. Class: |
606/159; 604/22; 606/170 |
Intern'l Class: |
A61B 017/20 |
Field of Search: |
606/159,170,180
604/22,95,264,267
|
References Cited
U.S. Patent Documents
4728319 | Mar., 1988 | Masch | 604/22.
|
4883458 | Nov., 1989 | Shiber | 604/22.
|
Primary Examiner: Hafer; Robert A.
Assistant Examiner: Owens; Kerry
Attorney, Agent or Firm: Shiber; Samuel
Parent Case Text
CROSS REFERENCE TO OTHER APPLICATIONS
This application is a continuation in part (CIP) of application Ser. No.
07/286,509 filed 12/19/88 (now U.S. Pat. No. 4,894,051) which is a CIP of
application Ser. No. 07/243,900 filed 9/13/88 (now U.S. Pat. No.
4,886,490) which is a CIP of three applications, application Ser. No.
07/078,042 filed 7/27/87 (now U.S. Pat. No. 4,819,634) application Ser.
No. 07/205,479 filed 6/13/1988 (now U.S. Pat. No. 4,883,458) and
application Ser. No. 07/225,880 filed 7/29/88 (now U.S. Pat No.
4,842,579). These three applpications are CIPs of application Ser. No.
07/018,083 filed 2/24/1987 , which is a CIP of application Ser. No.
06/874,546 filed 6/16/1986 (now U.S. Pat. No. 4,732,154) which is a CIP of
application Ser. No. 06/609,846 filed 5/14/1984 (abandoned).
All the above applications are being incorporated herein by reference.
Claims
I claim:
1. An atherectomy system for cutting an obstruction in a patient's vessel,
comprising in combination:
a flexible guide-wire insertable into the vessel,
a flexible rotary-catheter being rotatably disposed and insertable into the
vessel, over said flexible guide-wire,
a cutting means, at a distal end of said flexible rotary-catheter, for
cutting said obstruction,
coupling means at the proximal end of said flexible rotary-catheter for
engaging a drive means having a motor,
wherein at least one torque limiting clutch is interposed between said
motor and said cutting means, limiting the torque transmitted distally.
2. An atherectomy system as in claim 1, wherein said torque limiting clutch
is interposed between a proximal section of said flexible rotary-catheter
to a distsal section of said flexible rotary-catheter.
3. An atherectomy system as in claim 1, wherein said drive means have a
hollow shaft through which said guide-wire can pass and extend, a distal
end of said hollow shaft engagable with said coupling means,
a motor coupled to said hollow shaft through torque limiting clutch.
Description
BACKGROUND AND SUMMARY OF THE INVENTION
With age a large percentage of the population develops atherosclerotic
arterial obstructions resulting in a diminished blood circulation and a
variety of related disorders. Presently such obstructions are circumvented
by surgically grafting a bypass or they are treated by a catheter equipped
with a balloon which is inserted through the arterial system, over a
flexible guide-wire, into the obstruction and then inflated to expand the
obstruction's lumen (Angioplasty). Some of the problems with Angioplasty
are that it injures the arterial wall, it creates a rough lumen and in
substantial number of the cases it is ineffective. Further, Angioplasty
does not capture and remove the obstruction material out of the arterial
system, therefor Angioplasty carries the risk of dislodging obstruction
material and allowing it to move down stream creating additional
blockages.
An objective of the present invention is to provide an over a guide-wire
rotary Atherectomy catheter system, which cuts and removes the obstruction
material and which is equipped with torque limiting clutch means to
prevent damage to the arterial system. The system may be introduced into
the arterial sytem at the groin area, through a sheath to reach a work
site in the coronary arteries, which requires a long catheter with an
elastic, supple, distal section, a stable diametrical cross section and a
torque transmitting ability through the various arteries it is passed
through. Meeting these design objectives simultaneously, limits the
strength of the distal section (as shown in FIG. 1, the atherectomy system
comprises several elongated parts in a nested relationship, and their ends
or sections shall be referred to as "distal" meaning the end which goes
into the vessel and "proximal" meaning the other end, thus, "distal
direction" or "distally" shall indicate a general direction from the
proximal end to the distal end, and "proximal direction" or "proximally"
shall refer to an opposite direction).
The rotary cutting action which takes place at the distal end of the
flexible rotary-catheter requires a certain amount of net torque and
rotation. To provide it, the flexible rotary-catheter is driven at its
proximal end by a motor, however, due to frictional losses along the
length of the flexible rotary-catheter the gross torque that is required
at the proximal end is substantially larger than the net torque. To
withstand the gross torque the proximal section is strengthened, for
example, by increasing its wall thickness or by reinforcing it, and since
the proximal section is often disposed in relatively straight arteries,
its increased stiffness is acceptable. However, due to various
unpredictable and uncontrollable variations that may occur during an
individual procedure, such as changes in coefficient of friction between
the rotating parts of the system and the stationary parts of the system or
of the artery, or changes in the forces inducing the friction which may
occur due to misalignment of parts of the system, or a spasm in the artery
which may lock the artery onto the rotary catheter, the pattern of torque
distribution along the frc may be altered, and it is an important
objective of this invention, even under such circumstances, to protect the
arteries against injury by either over torquing the artery directly or by
over torquing and fracturing the flexible rotary-catheter which may in
turn cause injury to the artery.
A numerical example may be helpful: Assuming that the required net and
gross torques are 1 inch-ounce and 5 inch-ounce, respectively, and that
the ultimate strength of the distal and proximal sections is 3 inch-ounce
and 9 inch-ounce, respectively, and further assuming that the motor drive
can deliver 7 inch-ounce at stall but because of inherent torque/speed
characteristics it will deliver as much as 12 inch-ounce while turning.
Thus, it can be seen that if due to an arterial spasm or other cause the
blade became locked in the artery, even momentary, the motor may deliver
close to 12 inch-ounce of torque to the blade (as previously discussed the
frictional losses along the flexible rotary-catheter may occasionally be
very small) fracturing the distal section, causing serious complications.
If the spasm occurs at a point along the proximal section it can have the
same undesirable results. To prevent such complications a first torque
limiting clutch rated at 2 inch-ounce is interposed between the distal
section and the proximal section and a second torque limiting clutch rated
at 6 inch-ounce is interposed between the motor and the drive's output
shaft. The first torque limiting clutch enables sufficient working torque
to be transmitted to the distal section but prevents destructive torque
from reaching it; the second torque limiting clutch does the same for the
proximal section.
BRIEF DESCRIPTION OF THE FIGURES
FIG. 1 schematically shows a general view of an atherectomy system
according to the present invention, introduced into an arterial system of
a patient to cut and remove an obstruction in his heart's artery. The
heart outline is shown in phantom lines.
FIG. 2 shows, on a larger scale, a distal section and a part of the
proximal section of the flexible rotary-catheter, with a torque limiting
clutch interposed between the sections.
DETAILED DESCRIPTION OF THE FIGURES
FIG. 1 schematically shows a general view of the atherectomy system 10
inserted at the groin area of a patient through a sheath 32, through his
arterial system 11 into a coronary artery 12 for removing an obstruction
13 therefrom. The system 10 comprises:
A flexible guide-wire 14, insertable into the vessel,
a flexible rotary-catheter 15, rotatably disposed and insertable into the
vessel, over the flexible guide-wire,
a cutting means 16, at a distal end of the flexible rotary-catheter, for
cutting the obstruction,
coupling means 17 at the proximal end of the flexible rotary-catheter
defining a tapered seat for engaging a drive means 120.
A first torque limiting clutch 18, shown also in FIG. 2, is interposed
between proximal and distal sections 19 and 20, respectively, of the
flexible rotary-catheter. The clutch 18 is formed by fitting the proximal
end of section 20 into the distal end of section 19 to establish
frictional engagement between the two sections which limits the torque
capacity of the clutch to a certain permissible value beyond which the
clutch slips, thereby limiting the torque that is transmitted distal to
the clutch and protecting the distal section from damage by an occasional
transfer of higher torques that may be applied to the proximal end of
section 19. A lock-ring 24 formed on section 20 which fits in a
corresponding groove 24' defined by section 19, prevents a relative
longitudinal displacement between the sections but allows them to rotate
relative to one another when the clutch slips.
The drive means 120 has a housing 43 which rotatably supports a hollow
shaft 21 through which the guide-wire passes and extends, the distal end
of the hollow shaft has a taper for fitting into and engaging with the
tapered seat of the coupling means. A motor 22 is coupled to the hollow
shaft through a second torque limiting clutch 23. The clutch 23 is made of
a gear wheel 25 which is sandwiched between and frictionally engaged with
a shoulder 26 formed on the shaft and a pressure plate 27 which is
energized against the gear wheel by a compression spring 28 which is
supported by a flange 29 which is affixed to the shaft. A pinion 30 which
is connected to and driven by the motor 22 is engaged with the gear wheel.
The clutch limits the torque delivered to the shaft by the gear wheel 25
by sliding between the shoulder and pressure plate when certain torque is
reached, thereby limiting the torque that the drive 120 transmits to the
proximal section.
A battery 33 is wired to the motor through a switch 37 by wires 34, 35 and
36. When the switch is depressed it completes an electrical circuit which
supplies electrical current to the motor to drive it.
The housing 43 defines an annular cavity 40 and a passage for connecting
the hollow shaft to a port 42 for introducing suction or fluids into the
flexible rotary-catheter through the hollow shaft. A seal 41 seals the
annular cavity while allowing the flexible guide-wire to slidingly extend
through the hollow shaft and out of the housing.
The atherectomy system can be manufactured in different diameters and
lengths depending on the size and site of artery that it is intended for
and on whether the system is to be used percutaneously (that is through
the skin) or intra-operatively (that is when the vessel is surgically
exposed for inserting the system into the vessel).
While the present invention has been illustrated by one embodiment, it
should be understood that various modifications and substitutions may be
made without departing from the spirit of the invention or the scope of
the claims.
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